Conventional thermal transfer printers typically supply a record medium, such as a paper sheet, together with a thermal transfer recording ribbon to a print section. When the record medium and the film are thus disposed at the print section, thermal print heads are then selectively driven in response to print information so that portions of the thermally transferable ink on the ribbon will be melted and thence transferred onto the record medium. As can be appreciated, during subsequent feeding and handling of the printed sheets, mechanical abrasion of the print areas will occur presenting a problem that the printed information upon the record medium will be smeared thereby deleteriously affecting the print quality. Also, mechanical abrasion during processing and/or the subsequent handling of printed material may cause the print quality to fade thereby deleteriously affecting the print resolution. As such, there exists a need to prevent degradation of the printed information upon a record medium and it is towards this need that the present invention is directed.
In accordance with the present invention, a thermal transfer printing ribbon is provided having a base film coated with a plurality of transfer printing ink regions which are spaced-apart from one another in the longitudinal direction of the ribbon--that is, the direction in which the ribbon will be fed to a print section in a thermal transfer apparatus. Each transfer printing ink region can be comprised of a single color or can be subdivided into selected regions of different colors so as to permit multi-colored inks to be transferred to the record medium. Interposed between the adjacent pairs of the colored print ink regions, there is provided a region of transparent protective ink which itself is also thermally transferable.
Accordingly, by conveyance of a record medium to a print section having plural selectively operable thermal print heads, the visible or colored print ink can be thermally transferred to selected portions of the record medium by the selective operation of the thermal print heads. The present invention then subsequently permits the thermal transfer of the protective transparent ink so that the transferred transparent ink is overlaid upon the transferred colored ink on the record medium. As such, the information printed upon the record medium by means of the transferred colored ink will be visible through the layer of transferred transparent ink superposed thereupon while, at the same time, the layer of transferred transparent ink will provide protective functions against mechanical abrasion thereby maintaining the print quality and print resolution of the record medium.
The above advantages of the present invention, as well as others, will become more clear to the reader after careful consideration is given to the detailed description of the presently preferred exemplary embodiments thereof which follow.